Best Propulsion Device for 60 knots

[RANCHI OTTO]

I need an advice concerning a choiche:

Which is the best piercing screws propulsion device for a craft having 60 knots speed ?

I would say Arneson..but what about Trimax, Sea Fury, Sea Rex, Levi Drive...

Did you have some opinions...?

Thanks

[tom kane]

According to the experts fast boats (60 knots) spend more time going slow than going fast.A dedicated surface propulsion just for speed would not be plesant to use but good for racing.Sea conditions make you slow down or stay in port.Look for a surface drive that offers the best for all boating conditions (if you can find one) for the intended use of the boat.You probably will need to build your own to get something that does work allround conditions.

[RANCHI OTTO]

The boat is an interceptor and the 60 knots are imperative!

All mechanical items at 60 knots (continuous speed) are under stress and my question was...It's the Arneson the best soluntion?...or..

[fede]

Ciao Otto,as far as I know Arneson is a great propulsion system but the fin in front of the prop creates serious problems of spinout sometimes at hig hspeeds,it is not very common on race courses.
Try to choose a system that has the fin behind the prop.
Trimax might be the best choice.
I kow the levi drive and spoke with a sales person at the genova show, I'm quiet convinced that they are not a good choice for ultra high speed apps,they are better suited to high speeds bet. 30 and 50 kn. and I thin kthis is because of the big tube/double fin that is down in water.
I suggest that you take a look at what is an evolution of the Levi drive,it is called flexidrive made by victory design.
http://www.flexitab.com/flexidrive.htm
In particular have a look to the flexidrive speed which is trimmable.
A good choice which I feel is not very considered outside races is also an IMCO or Mercruiser racing system,like the SSM with an extension box,it is the most used system in racing apps. and I don't see why it should not be fine for military apps. (am I missing something? )
Also take a look at pulse drive,it is a nice system too.
You should also consider the new Jolly Drive Special (made in Italy) system which is proving to be a good choice too.

[fede]

http://www.boatdesign.net/gallery/sh...3/limit/recent

[RANCHI OTTO]

No..I don't think so.
This kind of boats are practically running out of water and the resistance of the sterndrive is low..but I have a boat with a displacement of 19.5t...

The propulsion device is well working in water and the boat is never jumping in water ....

The power to be installed is of 2 x 1500 bhp abt.....

[RANCHI OTTO]

Fede! The Jolly Drive has his fin located at the same place like the Arneson....

[fede]

Ciao Otto, with 1500 hp per engine you don't have many choices...
I've not seen the Jolly Drive "SPecial" yet but I know it's different from the older one (which in fact is very similar to Arneson)

[RANCHI OTTO]

Ciao Fede,

what about the SUPER-RIB?

[fede]

The RIB will race its first competion next week in Cesenatico,8th-9th july.
Untill now we have reached a max speed of 69.5 knots,I expect to reach the 70 barrier with a 27 prop (we are now using a 26) my goal is 74, and this could be achieved raising the prop height and using an extension box.
This championship will be "used" to test the boat, I do not expect and do not care about any result,from october we'll start making modifications to improve the boat.

[buckknekkid]

otto, are you trying to solve the age old BAR to BARI situation?

[RANCHI OTTO]

Buckknekkid, please my english knowledges are not so good to understand what do you mean...please clarify....
Thanks!

[buckknekkid]

there are many builders in Bar Montengro who have worked on the same issue for many years. Trimax always seems to come up.

[RANCHI OTTO]

Where is BAR MONTENGRO? Do you mean MONTENEGRO...?

I've installed trimax on boats but the fixed one...I think that there is the possibility to trim it with a new model..

Anyway this is a fast interceptor for the custom of Asia country...nothing to do with what do you were meaning...

[Tim B]

I know you are thinking of surface drives, but a 60 Kts is the top-end for a jet-drive. You may want to consider looking for a good water jet, as this will give you better efficiency and more control at low speed. Especially if you are trying to move quite a lot of boat. Also, you get rid of the vulnerable propellor.

It may be impracticle for your situation, but it's worth considering,

Tim B.